The present invention relates generally to mounting an electrical receptacle on a substrate and more particularly to mounting a banana type receptacle to a circuit board for use in electronic instruments, such as power supplies, hand-held multimeters, oscilloscopes, time domain reflectometers, and the like.
Banana type leads are used in the electronic industry for coupling signals to and from a device under test. A typical banana lead has a single wire terminated at each end with a male banana plug. The banana plug has an elongated conductive probe portion wrapped with a barrel spring, so that the probe portion may be inserted into a banana receptacle in an instrument. The banana receptacle has a conductive sleeve that makes contact with the barrel spring and is surrounded by electrically insulating material on the bottom and outer surface of the conductive sleeve.
Underwriters Laboratories, UL, has established insulation standards for electronic measuring and testing equipment (UL1244) that establishes minimum distances between conductive elements and users for preventing hazardous electrical shocks. Banana type leads that meet this standard have a tubular shaped shroud enclosing the male banana plug. The shroud is a thin walled cylinder of insulating material that provides the minimum distance separation between the male plug, coaxially disposed within the shroud, and the user. The corresponding banana receptacle may include an outer ring of insulating material defining an annular bore coaxial with the insulated conductive sleeve. The shroud of the male plug fits into the annular ring of the receptacle with the male plug making electrical contact with the conductive sleeve.
The conductive sleeve of the banana receptacle generally has electrical leads extending from the sleeve that are exposed at the bottom of the receptacle. The electrical leads are of a length that allows them to be inserted into electrically conductive apertures in a substrate, such as a circuit board. Conductive runs formed on the substrate couple the conductive apertures, and thus the conductive sleeve, to additional circuitry on the substrate. A particular problem with this type of banana receptacle is that the receptacle defines and controls the position of the circuit board in any hand-held electronic instrument design, and thus the overall design of the instrument. For example, the height of the receptacle defines the minimum thickness for the instrument for at least that portion of the instrument where the receptacle is positioned. A more complex shell design having differing surface levels is required if the instruments thickness is to be less than the minimum thickness associated with the receptacle. If, on the other hand, a flat surface shell is chosen, then the internal circuitry design may become more complex and expensive. For example, a custom display having a thickness matching the height of the receptacle may be required if the display is to be mounted directly onto the circuit board. Conversely, if the thickness of the display does not match the receptacle height, then conductive contact elements or cabling would be required for connecting the display to the circuit board which adds cost to the instrument. Likewise, buttons and knobs associated with most hand-held electronic instruments would be affected by the circuit board positioning problem.
An alternative to the above described receptacle-circuit board positioning problem is to remove the receptacles from the main circuit board. The receptacle or receptacles may be individually connected to the main circuit board via soldered wire connections between the receptacle leads and the circuit board. The receptacle or receptacles may also be bolted to the circuit board or instument case with wire leads connecting the receptacle to the circuit board. The receptacle or receptacles may further be placed on a separate circuit board and electrically connected to the main circuit board via soldered wire connections between the leads of the receptacle(s) and the main circuit board or providing some form of interconnect between the boards. While this solution frees designers from the receptacle-circuit board positioning problem, it adds component and manufacturing costs to the instrument.
What is needed is a method of mounting an electrical receptacle, such as a banana receptacle, on a substrate, such as a circuit board, without the limitations of previous receptacle-circuit board designs. The mounting method should not add component or manufacturing costs to the instrument and should be compatible with automated circuit board manufacturing processes. The method should further be flexible to allow for positioning the electrical receptacle at any height within the circuit board. Additionally, the method should also be flexible for permitting the positioning of the circuit board containing the electrical receptacle anywhere within the shell of the instrument.
Accordingly, it is an object of the present invention to provide a method for mounting an electrical receptacle on a substrate that is compatible with automated circuit board manufacturing processes, such as wave soldering.
It is another object of the present invention to provide a method of mounting an electrical receptacle on a substrate that does not add significant component or manufacturing costs to an electronic measurement instrument, such as a hand-held digital multimeter, time domain reflectometer, oscilloscope, or the like.
It is a further object of the present invention to provide a method for mounting an electrical receptacle on a substrate that allows positioning of substrate within an electronic measurement instrument, such as a hand-held digital multimeter, time domain reflectometer, oscilloscope, or the like.
The method of mounting an electrical receptacle on the substrate includes the steps of placing the electrical receptacle over an aperture formed in the substrate with the receptacle having a body of electrically insulating material partially surrounding an electrically conductive element having a deformable electrical lead with the body of electrically insulating material having support ribs formed on an exterior surface of the insulating body supporting the receptacle over the aperture and the electrical lead making an electrical connection with an electrical contact on the substrate. The electrical lead is affixed to the electrical contact and the receptacle is inserted into the substrate. The affixing step further includes the step of soldering wherein the preferred embodiment of the soldering step further includes the step of wave soldering. The wave soldering step further includes the steps of applying a solder flux to the substrate and heating the substrate prior to the soldering step. The inserting step further includes the step of deforming the electrical lead as the receptacle is inserted into the aperture. The inserting step further includes the steps of shearing or deforming the support ribs and positioning shoulders of alignment ribs, formed on the exterior surface of insulating body, against the substrate. Alternately, the inserting step may further include the steps of deforming the support ribs and positioning shoulders of alignment ribs, formed on the exterior surface of the insulating body, against the substrate.
The objects, advantages and novel features of the present invention are apparent from the following detailed description when read in conjunction with the appended claims and attached drawings.